The present invention relates to a pattern configuration measuring apparatus for measuring a three dimensional configuration, of an LSI fine pattern, such as a pattern taper angle, film thickness (depth), cross sectional profile, pattern dimension and the like.
As a technique for measuring a three dimensional configuration of a fine pattern by using a scanning electron microscope (hereinafter called a SEM), a cross section observing method heretofore widely used is known whereby a specimen is cut away to observe its cross sectional profile.
A system is also known wherein images are taken with a SEM at different stage tilting angles, and manual matching of corresponding positions of the images is carried out for calculation of a three dimensional configuration (refer to Y. Kato et al.: "Stereoscopic Observation and Three Dimensional Measurement for Scanning Electron Microscopy" IITRI/SEM/1977, pp. 41 to 48, and Hama et al.: "Determination of Three Dimensional Image Information Based on A Stereoscopic Photograph Taken with Ultra High Voltage Electron Microscope" Electron Microscopy, Vol. 20, No. 2, 1985, pp. 134 to 142).
A system is also known wherein signals detected with two detectors disposed symmetrically relative to the center of a beam radiated position are processed and integrated for calculation of a three dimensional configuration (refer to T. Suganuma: "Measurement of Surface Topography Using SEM with Two Secondary Electron Detectors" J. Electron Microscopy., Vol. 34, No. 4, pp. 328 to 337, 1985).
Although the cross section observing method is widely used, the specimen once cut-away cannot be used again. In addition, the pattern to be measured is limited to the cross sectional pattern at the cut-away plane. There is also for an associated problem that the cross sectional pattern of a fine hole having a diameter of, e.g., 2 microns or smaller, it becomes difficult to obtain a correct image of an actual pattern unless the cut-away plane is made perpendicular to the substrate surface.
The method whereby a stereoscopic configuration is calculated by obtaining corresponding points of images taken with an SEM at different stage tilting angles has been widely used in the field of remote sensing. With this method, obtaining the corresponding points, i.e., manually performing so-called pattern matching, takes a considerably long time. On the other hand, automatically performing pattern matching may cause matching errors which are not negligible depending upon the configuration of a fine pattern, resulting in a large measurement error.
For processing signals from two detectors disposed symmetrically relative to the center of a beam radiated position, it is necessary to balance beforehand the signals from both the detectors. In addition, it is necessary to vapor-deposit Au beforehand on a specimen because a high S/N ratio is required. Furthermore, if a pattern to be measured is isolated from other patterns, a good stereoscopic configuration can be obtained, however if adjacent patterns are spaced by 2 microns or less, the resultant stereoscopic configuration is influenced by the adjacent patterns and becomes different from the actual configuration.